The assignee of the present invention designs and manufactures spacecraft for communications and broadcast services. The spacecraft are carried into space, into a transfer orbit or an operational orbit, for example, by a launch vehicle.
It is sometimes desirable to configure two or more spacecraft for simultaneous launch on a single launch vehicle. US patent publication number 2016/0304219, assigned to the assignee of the present invention, and hereby incorporated by reference in its entirety into the present application, discloses a stacked launch configuration where at least a portion of orbit raising is performed with the two or more spacecraft coupled together and allocation of orbit raising capability between the two or more spacecraft is optimized.
FIG. 1 illustrates an example of two spacecraft configured to be launched within a common fairing 1001 of a launch vehicle (not illustrated). A lower spacecraft 100(1) includes an adapter 107(1) that is mechanically coupled, in the launch configuration, with a primary payload adapter 1002 that may be part of an upper stage (not illustrated) of the launch vehicle. The lower spacecraft 100(1) includes an inter-spacecraft coupling arrangement 109 that is mechanically coupled, in the launch configuration, with an adapter 107(2) of an upper spacecraft 100(2).
The spacecraft may include on-board propulsion subsystems to perform orbit transfer maneuvers. For example the on-board propulsion subsystems, including chemical and/or electric thrusters, may be configured to execute orbit raising maneuvers to transfer the spacecraft from a launch vehicle transfer orbit (or “parking orbit”) to an operational orbit, for example, to a geosynchronous orbit. The on-board propulsion subsystems may also be configured to perform stationkeeping and for attitude control/momentum management purposes. For a stacked launch configuration such as illustrated in FIG. 1, at least a portion of orbit transfer maneuvers may be performed with the two or more spacecraft coupled together.
The spacecraft thrusters may be broadly categorized as either “chemical” or “electric” based on the respective primary energy source. Chemical thrusters, for example bipropellant thrusters, deliver thrust by converting chemical energy stored in the propellant to kinetic energy delivered to combustion products of the chemical propellant, e.g., a fuel such as monomethyl hydrazine and an oxidizer such as dinitrogen tetroxide.
A propulsion system may include chemical thrusters of diverse thrust levels for different mission phases. For example, orbit transfer maneuvers may be performed with a relatively high thrust chemical thruster, with a nominal thrust rating of, for example, 300 Newtons (N) or greater. Such a thruster may be referred to herein, and in the claims as a “high thrust chemical thruster” or as a “main satellite thruster” or MST. In addition, the propulsion system may include other chemical thrusters for stationkeeping and attitude control delivering, advantageously, relatively low thrust, for example a nominal thrust rating of less than 30 N and/or electric thrusters having a nominal thrust rating of less than 1 N for orbit transfer and/or stationkeeping.